An oil pump for an engine used in a vehicle includes a rotor that revolves and an oil pump housing that encases the rotor. The rotor and oil pump housing are generally formed from material such as iron (cast iron), billet steel, powdered metal, aluminum, or the like.
In conventional oil pumps, an inner drive gear is typically formed with one less gear-tooth than an outer driven gear. When the inner drive gear and the outer driven gear engage each other and spin, the inner drive gear rotates one gear-tooth faster than the outer driven gear per cycle. During the execution of a single complete cycle or revolution of the drive gear, a cavity is formed between each of the drive gear-teeth and the driven gear-teeth. The cavity gradually and consecutively expands on the intake side and contracts on the exhaust side as the drive gear and driven gear rotate.
The typical oil pump also includes a housing that has an oil intake port, an oil exhaust port, and an isolated housing portion. Theoretically, oil is taken up between teeth of the drive gear and driven gear and compressed into a cavity between these teeth. Initially the cavity is in an expanding state, the cavity between each of the drive gear teeth and the driven gear teeth then contracts as the gears rotate and discharge the oil into the oil discharge port. Thus, the oil is taken in from the oil intake port, compressed between the teeth of the drive gear and driven gear and delivered to the oil discharge port.
Typically, the end portion of the oil intake groove and the start portion of the oil exhaust groove are configured to be separated from one another. An isolated housing portion may disposed between the oil intake and oil discharge ports in order to separate the oil intake port and oil discharge port. A drawback in the typical oil pump design is that the exterior surface of the outer drive gear and the inner surface of the housing unit experiences wear and friction at that interface due to the various loads experienced between the outer driven gear and the housing. The aforementioned condition lowers the durability of the housing and increasing oil leakage through clearance between the meshing gear-teeth.